This invention relates in general to preventing the production of particulate materials through a wellbore traversing an unconsolidated or loosely consolidated subterranean formation and, in particular, to an apparatus and method for obtaining a substantially complete gravel pack within an interval of the wellbore.
Without limiting the, scope of the present invention, its background is described with reference to the production of hydrocarbon fluids through a wellbore traversing an unconsolidated or loosely consolidated formation, as an example.
It is well known in the subterranean well drilling and completion art that particulate materials such as sand may be produced during the production of hydrocarbons from a well traversing an unconsolidated or loosely consolidated subterranean formation. Numerous problems may occur as a result of the production of such particulates. For example, the particulates cause abrasive wear to components within the well, such as tubing, pumps and valves. In addition, the particulates may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids by processing equipment at the surface.
One method for preventing the production of such particulate material to the surface is gravel packing the, well adjacent to the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a sand control screen is lowered into the wellbore on a workstring to a position proximate the desired production interval. A fluid slurry including a liquid carrier and a particulate material known as gravel is then pumped down the workstring and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.
The liquid carrier either flows into the formation or returns to the surface by flowing through the sand control screen or both. In either case, the gravel is deposited around the sand control screen to form a gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the particulates carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of particulate materials from the formation.
It has been found, however, that a complete gravel pack of the desired production interval is difficult to achieve particularly in long or inclined/horizontal production intervals. These incomplete packs are commonly a result of the liquid carrier entering a permeable portion of the production interval causing the gravel to form a sand bridge in the annulus. Thereafter, the sand bridge prevents the slurry from flowing to the remainder of the annulus which, in turn, prevents the placement of sufficient gravel in the remainder of the annulus.
Prior art devices and methods have been developed which attempt to overcome this sand bridge problem. For example, attempts have been made to use devices having perforated shunt tubes or bypass conduits that extend along the length of the sand control screen to provide an alternate path for the fluid slurry around the sand bridge.
It has been found, however, that shunt tubes installed on the exterior of sand control screens are susceptible to damage during installation and may fail during a gravel packing operation. Also, it has been found that to cost of fabricating such shunt tube systems is high. In addition, it has been found, that it is difficult and time consuming to make all of the necessary fluid connections between the numerous joints of shunt tubes required for typical production intervals.
Therefore a need has arisen for an apparatus and method for gravel packing a production interval traversed by a wellbore that overcomes the problems created by sand bridges. A need has also arisen for such an apparatus that is not susceptible to damage during installation and will not fail during a gravel packing operation. Further, a need has arisen for such an apparatus that is cost effective and not difficult or time consuming to assemble.
The present invention disclosed herein comprises an apparatus and method for gravel packing a production interval of a wellbore that traverses an unconsolidated or loosely consolidated formation that overcomes the problems created by the development of a sand bridge between a sand control screen and the wellbore. Importantly, the apparatus of the present invention is not susceptible to damage during installation or failure during the gravel packing operation, is cost effective to manufacture and is not difficult or time consuming to assemble.
The apparatus comprises a sand control screen that is positioned within the wellbore and a tubular member disposed around the sand control screen forming a first annulus with the sand control screen and a second annulus with the wellbore. The tubular member has an axially extending production section with a plurality of openings and an axially extending nonproduction section with a plurality of outlets. A channel, that is disposed within the first annulus, is substantially circumferentially aligned with the nonproduction section of the tubular member to form a slurry passageway.
The channel has a web and a pair of oppositely disposed sides that from an angle with the web of between about 45 and 90 degrees. The ends of the sides may be square or may be rolled. In either case, the sides contact the inner surf ace of the tubular member when the pressure within the slurry passageway is below a predetermined value.
When the pressure within the slurry passageway is above the predetermined value, however, the sides will separate from the inner surface of the tubular member to relieve pressure. The pressure relief capability is allowed as the channel is attached to the tubular member with attachment members that connect the web of the channel to the tubular member leaving the sides free to deform. Alternatively, the channel may be connected to the sand control screen.
In some embodiments, the tubular member will have more than one axially extending production section and more than one axially extending nonproduction section. In these embodiments, a channel corresponds to each of the nonproduction sections such that more than one slurry passageway is created.
One method for gravel packing an interval of a wellbore of the present invention comprises traversing a formation with the wellbore, locating a sand control screen within the wellbore proximate the formation, positioning a tubular member within the wellbore forming a first annulus with the sand control screen and a second annulus with the wellbore, disposing a channel within the first annulus such that the channel is substantially circumferentially aligned with a nonproduction section of the tubular member forming a slurry passageway, injecting a fluid slurry containing gravel through the slurry passageway such that the fluid slurry exits the slurry passageway through outlets and terminating the injecting when the interval is completely packed with the gravel.
This method may also include contacting the sides of the channel with an inner surface of the tubular member when the pressure within the slurry passageway is below a predetermined value and relieving pressure from the slurry passageway by allowing the sides of the channel to temporarily separate from the inner surface of the tubular member when the pressure within the slurry passageway is above the predetermined value.
Accordingly, the apparatus and method of the present invention overcome the problems associated with the formation of sand bridges. Specifically, if a sand bridge forms, the fluid slurry bypasses the sand bridge by traveling within the apparatus of the present invention. Thereafter, the fluid slurry exits the apparatus of the present invention allowing the gravel in the slurry to be deposited in the second annulus such that a complete gravel pack of the interval can be achieved.